DTC P0351: Ignition Coil "A" Primary Control Circuit/Open: Notes

DTC detecting condition:

Immediately at fault recognition

Trouble symptom:

Improper idling
Poor driving performance

CAUTION: Use the check board when measuring the ECM terminal voltage and resistance. Ref. to ENGINE (DIAGNOSTICS) (H4DOTC)>GENERAL DESCRIPTION>PREPARATION TOOL>HOW TO USE CHECK BOARD .

NOTE: After the faulty parts are repaired or replaced, perform the final check in Basic Diagnostic Procedure. Ref. to ENGINE (DIAGNOSTICS) (H4DOTC)>BASIC DIAGNOSTIC PROCEDURE>PROCEDURE .

Wiring diagram:

Engine Electrical System Ref. to WIRING SYSTEM>ENGINE ELECTRICAL SYSTEM .

Courtesy of SUBARU OF AMERICA, INC.

CHECK IGNITION COIL POWER SUPPLY.
1. Turn the ignition switch to OFF.
2. Disconnect the connector from ignition coil.
3. Turn the ignition switch to ON.
4. Measure the voltage between ignition coil connector and engine ground.
  Connector and terminal.
  
  DTC P0351; (E31) No. 1 (+) - Engine ground (-):
  
  DTC P0352; (E32) No. 1 (+) - Engine ground (-):
  
  DTC P0353; (E33) No. 1 (+) - Engine ground (-):
  
  DTC P0354; (E34) No. 1 (+) - Engine ground (-):
Is the voltage 10 V or more?

Yes: Go to 2.

No: Repair the following item.
- Open circuit or short circuit to ground in harness between M/B and ignition coil connector
- Blown out of fuse
- Poor contact of coupling connector
- Poor contact of J/C
CHECK HARNESS OF IGNITION COIL GROUND CIRCUIT (OPEN).
1. Turn the ignition switch to OFF.
2. Measure the resistance of harness between ignition coil connector and engine ground.
  Connector and terminal.
  
  DTC P0351; (E31) No. 3 - Engine ground:
  
  DTC P0352; (E32) No. 3 - Engine ground:
  
  DTC P0353; (E33) No. 3 - Engine ground:
  
  DTC P0354; (E34) No. 3 - Engine ground:
Is the resistance less than 5 Ω?

Yes: Go to 3.

No: Repair the open circuit in harness between ignition coil connector and engine grounding terminal.
CHECK HARNESS BETWEEN ECM AND IGNITION COIL CONNECTOR (SHORT TO GROUND).
1. Disconnect the connector from ECM.
2. Measure the resistance between ignition coil connector and engine ground.
  Connector and terminal.
  
  DTC P0351; (E31) No. 2 - Engine ground:
  
  DTC P0352; (E32) No. 2 - Engine ground:
  
  DTC P0353; (E33) No. 2 - Engine ground:
  
  DTC P0354; (E34) No. 2 - Engine ground:
Is the resistance 1 MΩ or more?

Yes: Go to 4.

No: Repair the ground short circuit of harness between ECM connector and ignition coil connector.
CHECK HARNESS BETWEEN ECM AND IGNITION COIL CONNECTOR (OPEN).
Measure the resistance of harness between ECM connector and ignition coil connector.

Connector and terminal.

DTC P0351; (E158) No. 24 - (E31) No. 2:

DTC P0352; (E158) No. 37 - (E32) No. 2:

DTC P0353; (E158) No. 50 - (E33) No. 2:

DTC P0354; (E158) No. 63 - (E34) No. 2:

Is the resistance less than 1 Ω?

Yes: Go to 5.

No: Repair the open circuit in harness between ECM connector and ignition coil connector.
CHECK FOR POOR CONTACT.
Check for poor contact of ECM connector.

Is there poor contact of ECM connector?

Yes: Repair the poor contact of ECM connector.

No: Go to 6.
CHECK SPARK PLUG CONDITION.
1. Remove the spark plug of the corresponding cylinder. Ref. to IGNITION (H4DOTC)>SPARK PLUG>REMOVAL .
2. Check the spark plug condition. Ref. to IGNITION (H4DOTC)>SPARK PLUG>INSPECTION .
Is the check result OK?

Yes: Replace the ignition coil. Ref. to IGNITION (H4DOTC)>IGNITION COIL .

No: Replace the spark plug. Ref. to IGNITION (H4DOTC)>SPARK PLUG .